Effectiveness is the degree with which the same drug improves patients in the uncontrolled hurly-burly of everyday practice; data which are much more difficult to come by.
The information required for practice-based evidence is of three sorts: context (e.g. case mix), intervention (treatment) and outcomes (change).
On return to the UK she reflected on these data and produced new sorts of chart (she had trained in mathematics rather than "worsted work and practising quadrilles") to show that it was most likely that these excess deaths were caused by living conditions rather than, as she initially believed, poor nutrition.
Her reputation was damaged, however, when she and William Farr, Registrar General, collaborated in producing a table which appeared to show a mortality in London hospitals of over 90% compared with less than 13% in Margate.
As, however, its proper function is to restore the sick to health as speedily as possible, the elements which really give information as to whether this is done or not, are those which show the proportion of sick restored to health, and the average time which has been required for this object…"[11] Here she presaged the next key figure in the development of routine outcomes measurement Codman was a Boston orthopaedic surgeon who developed the "end result idea".
At its core was "The common sense notion that every hospital should follow every patient it treats, long enough to determine whether or not the treatment has been successful, and then to inquire 'if not, why not?'
"[12] He is said to have first articulated this idea to his gynaecologist colleague and Chicagoan Franklin H Martin, who later founded the American College of Surgeons, in a Hansom Cab journey from Frimley Park, Surrey, UK in the summer of 1910.
Perhaps because of instances of scandalously poor care (for example at the Bristol Royal Infirmary 1984-1995[17]) mortality data have become more and more openly available as a proxy for other health outcomes in hospitals,[18] and even for individual surgeons.
Therefore, as an indicator of the quality and safety of health care institutions, mortality remains important, but for individuals, it may not be the key goal.
In order to realise the full benefits of an outcomes measurement system we need large-scale implementation using standardised methods with data from high proportions of suitable healthcare episodes being trapped.
It has been argued that it is vital that the patient has been meaningfully involved in decisions about whether or not to embark on an intervention (e.g. a test, an operation, a medicine).
[30] Although a process rather than an outcome measure, the degree with which patients have been involved in shared decision making is clearly important.